Variation of pH and Electrical Conductivity Values of Different Deep Eutectic Solvents with Temperature

In this study, the variation of pH and electrical conductivity values of 6 different deep eutectic solvents (choline chloride-acetic acid, choline chloride-urea, choline chloride-citric acid, choline chloride-glycerol, choline chloride-lactic acid, and glycerol-citric acid) most likely to be used in food processes with temperature (25 °C, 50 °C and 75 °C) were investigated. The molar ratio was used as 1:1 for the glycerol-citric acid combination, and the molar ratio was applied as 1:2 for other solvents. Besides, 30% water by mass was added to all solvents. As a result, it was observed that the variation of pH values with temperature changed depending on the hydrogen bond donor type, while the electrical conductivity values increased in direct proportion to the increase in temperature. It was seen that linear model compatibility was high for both values. When the relations between pH and electrical conductivity values were examined, it was seen that deep eutectic solvent combinations formed with acid-based hydrogen bond donors showed a positive correlation, while other combinations showed a negative correlation. Finally, when the activation energies are examined, the combinations using citric acid as hydrogen bond donor for pH and urea for electrical conductivity have the highest value